Improvement in safety-valves



A.TURNBULL SAFETY-VALVE.

Patented April 17, 1877.

MPETERS. PHOYG-LITHOGRAPHgR. WASHINGON, D. C.

pressure continues in such excess.

' STA'rEs TENT OFF-116E? nnnxzrnnnn muennnnn, on GLASGOW, sooirLAnnJ A MR-prisms NET INASAFETYY-VALVES.

Specification forming part of Letters Patent No. I SQQSIGL dated April l7, 1877; application filed V I l i 7 March 7, 1877;, l

To all whom it may concern I Be it known that I, ALEXA NDER TURNscrew-nuts on theupper. ends:- of; rods/11,,

BULL, of Glasgow, in the county of Lanark,

Scotland, have invented .certain Improvements in Safety-Valves, of whichthe following is a specification My invention has for its object toconstruct a safety-valve so that when it opens, in consequence of thesteam or other fluid in the boiler or pipe, or other apparatus to whichit is applied, being in excess of that to which it is loaded, the actionof the steam or fluid, in

.escapiug, shall not diminish the effect of the steam in opening thevalve, or keeping it open to its full capacity as long as the internalMy improved safety-valves may be loaded in any of the ways in whichexisting safety-valves are loaded 5 and when loaded by springs they canbe proportioned so as to compensate for the increasing pressure of thesprings as they be come strained by the opening of the valves.

My improved safety-valve will open freely, so as to give a peripheraldischarge area equal to the total area for the passage of the steam orother fluid through the seat of the valve, and as this exceeds theeffective discharge area of ordinary safety-valves, it follows thatmyimproved valve may, for a given discharge, be made correspondinglysmaller than ordinary safety-valves.

My invention consists in making the valve in the form of an inverted cupor hollow cylin der, having a contraction near its lower end,

as more fully described hereafter.

In the accompanying drawings, Figures 1 and 2 are, respectively, a planand a'vertical section of myimproved safety-valve as loaded by a spring.I Thevalve-seat 3 is fitted into a hole in the bottom part 4 of acasting, 4 5 6, which can be fixed to a boiler or pipe, or otherapparatus containing steam or fluid the pressure of which is to belimited by means of the valve. The casting is in the form of a circularbase 4, connected, by pillars 5, to an upper annular part, 6, which lastis bored to act as a guide for the valve 7. "This valve7 is a hollowcylinder, the upper end of which is closed by or terminates in a cup, 8,to receive the bottom of a helical steel spring, 9. The spring 9 ishelddown by ani upper: plate, 10, fixed by screwed into the casing 45 6.The bottom end of the valve 7 is contracted, so that the annular partwhich bears on the seat 3 may be slightly less in diameter than theinterior of the valve. The contact-surfaces of the seat 3 and valve 7are shown flat; but they may be conical or spherical. The valve-seat 3has attached to it, by radial feathers, a central tube, 12, whichprojects up into the hollow valve 7, and has a collar formed on it nearits upper end. An annular block, 13, rests loosely on the collar on thecentral tube 12, and serves to check the communication between the upperpart of the hollow valve 7 and the lower part thereof near the outlet.This block 13, while nearly as large in diameter as the interior of thehollow valve 7, is not in any sense a closefitting piston, which wouldbe liable to stick and get out of order; besides, it is not at allnecessary for the action of the valve that it should fit like a piston.On the other hand, should the block 13, under any circumstances,

ever tend to move up or outward with the hollow valve 7, it would bequite free to do so, as

, it is not fixed to the central tube 12.

With the spring 9 applied as shown in the drawing, its pressure down onthe valve 7 will be greater the higher the valve is lifted,

owing to its being thereby more compressed.

This increased pressure of the spring will, however, be compensated forby action due to the interior of the valve 7, being larger in diameterthan the inner edge of the contactsurfaces of the valve and seat. Whenthe valve is shut the excess of pressure over that corresponding to theeffective area of the seat, and acting inside the valve on its upperend, will be balanced by the downward pressure on the inside of thecontraction 14 at the bottom of the valve; but when the valve is openedthe pressure downward on the contraction 14 will be diminished inconsequence of the vicinity of the contraction to the outlet pipe, whilethe full pressure, or at least a greater pressure than that acting onthe contraction 14:, will be maintained against the upper end of thevalve, and will continue to bear up the valve against the increasedpressure of thespring.

The central tube 12 serves to separate the center of the column of steamfrom the outer parts of that column, which latter parts rush toward theoutlet when the valve opens and become diminished in pressure; and tomake such separation more certain and complete, the tube 12 may becontinued downward to any reasonable extent. On the other hand, agreater pressure will be maintained in the center of the column of steamwhen the valve is open than at the outer parts, even without anyseparating-tube l2; and if, without that tube, the pressure oftheacenter of the column of steam is not sufficient on a certaininternal area of the tube 7, that internal area has simply to be made alittle larger.

What I claim as my invention, and desire to secure by Letters Patent, is

1. The combination, in a safety-valve, of the spring9 and valve-seat 3with the hollow valve 7, having the contraction 14 near the lower end,as and for the purpose described.

2. The combination of the valve-seat and the central tube 12 with theloaded hollow valves 7, having a contraction, 14, near the lower end, asspecified.

3. The combination of the valve-seat and loaded hollow valve with thecentral tube 12 and the annular block 13, resting on, but unconnectedwith, the said tube, as set forth.

ALEXANDER TURNBULL.

Witnesses EDMUND HUNT, LooK MOORE.

